I have evaluated the effects of selected persistent, inorganic pollutants on a series of insect systems. My first study examines the occurrence and consequences of environmental contamination with perchlorate. Perchlorate adversely effects some organisms, and has contaminated drinking or irrigation water in over half of the states in the USA, but data on insects is lacking. I therefore assessed the impact of water contamination with perchlorate and another contaminant, hexavalent chromium, on the mosquito Culex quinquefasciatus. The chronic levels of perchlorate and chromium causing mortality were 74 mg/L and 0.41 mg/L, respectively. Development was significantly effected at 25 mg/L perchlorate or 0.16 mg/L chromium. In combination, contaminants were synergistic, causing 14% more mortality than predicted.
I then examined the effect of perchlorate and hexavalent chromium on the widely used microbial mosquito control agents Bacillus thuringiensis subsp. israelensis (Bti) and directly, the additional stress on the larvae from even low levels of hexavalent chromium increased the efficacy of both Bti and Bsph by 21% and 80%, respectively. Thus, in the areas contaminated by hexavalent chromium, less of the microbial materials could be used to achieve suppression.
In a third experiment, I examined the effect of two contaminants, manganese and nickel, on the development and survival of an insect detritivore, Megaselia scalaris. Concentrations up to 2600 mg Mn/kg and 5200 mg Ni/kg did not reduce fitness of this fly, indicating that these detritivores have evolved to manage even exceptionally high concentrations sequestered in their food.
Lastly I investigated the acquisition of anthropogenic pollutants (perchlorate, selenium, manganese, and hexavalent chromium) by the invasive plant Tamarix ramosissima and its biological control agent Diorhabda elongata. All contaminants were accumulated by T. ramosissima and transferred to D. elongata beetles, though in some cases at lower levels than were found in the T. ramosissima host plants. Growth of D. elongata larvae was significantly reduced by Se contamination, but was not affected by the other pollutants. This is the first evidence that an anthropogenic pollutant can affect biocontrol programs.
|Advisor:||Trumble, John T.|
|School:||University of California, Riverside|
|School Location:||United States -- California|
|Source:||DAI-B 69/01, Dissertation Abstracts International|
|Subjects:||Organismal biology, Environmental science|
|Keywords:||Anthropogenic pollutants, Aquatic insects, Heavy metals, Perchlorate, Terrestrial insects|
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